1. Field of the Invention
The present invention relates to a semiconductor device comprising an insulated gate bipolar transistor, and a semiconductor circuit using the same.
2. Description of the Prior Art
Power semiconductor devices represented by an insulated gate bipolar transistor are used to control various power equipments. In a control circuit using this insulated gate bipolar transistor, it is necessary to put out a collector current by placing a limitation in order to indirectly detect a state of a load R.sub.L connected with the collector and also improve oscillation stability of a feedback circuit by entering a signal from the collector to the feedback circuit.
In such cases, the prior art, as shown in FIG. 6, is devised to draw out a limited current or voltage through a resistor R10 having high resistance from a control terminal 100. In FIG. 6, Z10 is a zener diode used to limit a voltage across the control terminal to less than a certain voltage and T1 is the insulated gate bipolar transistor.
Recently, a semiconductor device comprising an insulated gate bipolar transistor T1 as shown in FIG. 7 has also been proposed.
The semiconductor device shown in FIG. 7 uses a depletion type IGBT110 formed adjacent to the insulated gate bipolar transistor T1, in place of the resistor R10 of high resistance, therethrough attempting to detect a collector voltage.
That is, in the depletion type IGBT110, an n-type impurity is diffused in a channel region to form an n.sup.- depletion region 111, thus connecting a gate electrode 117 and an emitter electrode 119, which are disposed above the n.sup.- depletion region 111, by way of an opening formed on an insulating film 112. Consequently, a circuit as shown in FIG. 8 can thus be configured, in which the depletion type IGBT110 turns to be a state of ON even if a bias voltage between the gate electrode and the emitter electrode is zero (0), thereby drawing out the collector voltage or current.
However, there is a problem that the resistor of high resistance must be mounted separately in a circuitry of the prior art shown in FIG. 6 because it is difficult to form the resistor of high resistance integrally with the insulated gate bipolar transistor on the semiconductor substrate. With the construction of FIG. 7, there also is a problem of complicated step because a diffusing step is further required to form the n.sup.- depletion region 111.